One commercial process for making nitrous oxide involves the thermal decomposition of ammonium nitrate when heated from 200 to 260.degree. C. according to the following equation: EQU NH.sub.4 NO.sub.3 --N.sub.2 O+2H.sub.2 O
However, extreme caution must be used in handling ammonium nitrate, which may be highly explosive under extreme shock or elevated temperatures. Therefore, improved methods for controlling the thermal decomposition of ammonium nitrate have been disclosed. For example, the thermal decomposition of ammonium nitrate in the presence of a melt containing ammonium hydrogen sulfate and ammonium sulfate is described in U.S. Pat. No. 4,154,806; the thermal decomposition of ammonium nitrate into an aqueous, strongly acid reaction liquor containing chloride ions as a catalyst is described in U.S. Pat. No. 4,102,986; and the thermal decomposition of ammonium nitrate in a chloride-containing aqueous solution of nitric acid and the presence of catalytically active ions of manganese, copper, cerium, lead, bismuth, cobalt or nickel, is described in U.S. Pat. No. 3,656,899.
Another commercial process for producing nitrous oxide involves the reaction of ammonia and air using Mn and Bi oxides as catalysts. For example, Japanese Patent No. 6122507 describes a process for preparing nitrous oxide by the oxidation of ammonia with oxygen in the presence of steam and a CuO/MnO.sub.2 catalyst. Other methods for producing nitrous oxide include the reaction of a molten nitrate salt with ammonium chloride and the reaction of ammonia with at least one molten nitrate salt of an alkaline earth metal, as described in U.S. Pat. No. 4,720,377.
The present invention is directed to the conversion of ammonia with nitric oxide and/or oxygen into nitrous oxide using a catalyst comprising a Group VIB metal oxide. Accordingly, the present invention avoids the dangers associated with the use and handling of ammonium nitrate and is an alternative and novel nitrous oxide synthesis method that is inexpensive and safe.